study guide

EHST 3700 1

 Lab analytical techniques

 Dust and fibers – gravimetric, graticule, reticule

 Gas/vapor/metal dust and fumes

 Spectrophotometer

 Nephelometry

 Gas chromatography

 Mass spectrometry

 Absorption spectroscopy

 Inductively coupled plasma

 Fluorescence spectrometry

 Direct-reading methods

 Gas meters

 3 detectors – Wheatstone bridge circuit, metal-

oxide conductor, thermal conductor

 Photoionization and flame ionization detectors

 Detector or length-of-stain tubes

 Air sampling process

 Determining agents to be sampled  selecting

sampling method  obtaining adequate tools 

sampling  shipping  data analysis  reporting

EHST 3700/3701:

Industrial Hygiene

 To discuss the reasons for air sampling in the

workplace

 To explain the different types of sampling

strategies

 To describe some sampling methods for air

contaminants

 To describe analytical instruments and methods

in laboratories to evaluate air samples

 To interpret and evaluate air sampling results

 To discuss documentation of sampling events

 To discuss about sources of errors in sampling

 To discuss problems or limitations associated

with air samples

 Uses of Air Sampling

 Sampling Particulates

 Sampling Gases and Vapors

 Standard Sampling and Analysis Methods

 Laboratory Analytical Techniques

 Direct-Reading Methods

 Air Sampling Strategies

1. Determine agents to be sampled.

2. Select the sampling method.

3. Obtain and review a copy of the sampling

method.

4. Obtain adequate sampling media and

equipment.

5. Calibrate sampling pumps or instruments.

6. Perform sampling.

7. Ship samples to laboratory for analysis.

8. Interpret analytical results.

9. Prepare a report to employee and

management.

EHST 3700 2

 Should be methodical and documented on a

standardized form.

 Maximum risk employees

 Identify workers who are most likely to be

exposed to the highest levels of

contaminants

 Homogenous exposure group (HEG)

 Identify groups that have similar exposures

 By job title or function of the workers

 Random sampling from each HEG

 Field blanks

 Sample media that are exposed to the same

conditions as the media used for the actual

sampling, but are not connected to a sampling

pump

 10% of the total number of samples or at least 2

 Prepared and submitted with the samples for

analysis

 May indicate problems in sampling and handling

of the media

 May indicate previously unsuspected source of

interference or contamination

 Laboratory blanks

 Sample media that are not sampled on but

are prepared and analyzed by the laboratory

 Quality control taken to detect problems

with preparation and analysis of the samples

 Deducted from sample values (blank-

corrected)

 Sampling errors or bias (introduced by IH)

 Using inappropriate sampling media

 Using a direct-reading instrument outside of its

limitations and applications

 Use of incorrect flow rates

 Failing to perform calibrations or functional checks

on direct-reading instruments

 Overloading the sample collector

 Errors in calculations

 Sampling in the presence of interfering compounds

 Failure to follow special handling procedures

 Improper placement of sample collectors

 Neglecting to keep complete and accurate records

EHST 3700 3

 Laboratory errors

 Improper storage/handling of samples while

awaiting analysis

 Delays in analysis that exceed time limits for

stability of samples

 Use of incorrect analytical techniques

 Failure to properly prepare the samples for

analysis

 Contamination of samples with other samples or

lab chemicals

 Errors in calculations

 Mix-ups (i.e. incorrect labeling of samples)

 Loss of samples due to breakage, spillage, etc.

 Sampling and analytical errors (SAEs)

 Uncontrollable factors in most analytical

methods

 Numerical value used to evaluate whether

the sample results indicate exposures

within acceptable limits

 Air sampling data is not the actual absorbed

dose of the contaminant but as a

representation of a potential level of exposure.

 Variables affecting the absorbed dose:

 Age and gender

 Health status/ level of fitness

 Nature of work (sedentary or strenuous)

 Breathing rate

 Pre-existing health conditions, medications,

allergies

 Concurrent exposures (i.e. hobbies and non-

occupational sources)

 Whether or not the data are truly

representative of the airborne concentration

in the workplace

 Worst-case scenario

 Repeated sampling over a long period will

provide statistically more accurate data

regarding the actual concentrations

 Particulates – mass per unit volume

 Milligrams per cubic meter (mg/m3)

 Gases and vapors

 Parts per million (ppm)

 Parts per billion (ppb)

ppm =

C mg

m3 x 24.45

MW of contaminant

mg

m3 =

C ppm x MW of contaminant

24.45

 Convert from ppm to mg/m3

 Conc. of n-butyl acetate = 45 ppm

 MW = 116.2

 mg/m3

 Convert from mg/m3 to ppm

 Conc. of diphenyl = 12 mg/m3

 MW = 169

 ppm

=

C mg

m3 x 24.45

MW of contaminant

= C ppm x MW of contaminant

24.45

EHST 3700 4

 Air sampling process must be methodical and

documented.

 IH must understand the limits and errors in

air sampling.